Lymphoproliferative diseases involving B lymphocytes naturally infected with Epstein-Barr virus (EBV) are devastating complications of ablative cancer and transplantation therapies. Novel support therapies with stem cells and hematopoietic growth factors are increasingly being used, and ablative regimens are becoming more and more intensive. However, there is a suggestion that a number of malignancies, including EBV-positive lymphoproliferative disease, are on the rise. It has been difficult to discern the contribution of ablative therapies, immunodeficiency, and support therapies to the development of second malignancies because all elements are inseparable in the context of the patient. The present studies are intended to clarify the possible contribution of growth factors to the development of EBV-positive lymphoproliferative diseases. B cell immortalization by Epstein-Barr virus (EBV) and the continuous growth of B cells infected with EBV in vitro is dependent upon B cell secretion of growth factors in the culture supernatant and utilization of these factors by B cells infected with the virus. A major interest of the laboratory has been the identification of the compounds responsible for autocrine growth factor activity in EBV-immortalized cells and their role in B-cell immortalization/transformation. Initially we identified Interleukin-6 (IL-6) as one of the autocrine growth factors produced by EBV-immortalized B cells. Subsequently, we identified lactic acid as being another, more abundant and more potent autocrine growth factor produced by EBV-immortalized B cells. More recently, we have come to appreciate the existence of yet another autocrine growth factor activity produced by EBV-immortalized B cells, distinct from IL-6 and lactic acid. This molecule appears to be distinct from all other known growth factors, as assessed by testing panels of recombinant and natural molecules. Using standard purification techniques, we are in the process of purifying this molecule from serum-free supernatants of EBV-immortalized cells. We now know that anion exchange chromatography over Resourse Q, ion exchange chromatography over immobilized metal, gel filtration chromatography over S-100, and affinity chromatography over an anti-IFN antibody column are effective steps for enrichment of the activity we are pursuing. Our plan is to further develop product purification, obtain N-terminous and tryptic digestion-derived fragments sequences, clone, sequence and express at high level the gene coding for this novel B cell growth factor. With sufficient amounts of the purified recombinant protein we wish to pursue biochemical and functional characterization of this molecule. Tosato G, Taga K, Angiolillo A, Sgadari C. Epstein-Barr virus as an agent of Hematological Disease. In Viruses as agents of Hematological Disease. N.S. Young Ed. Balliere Clin Hematol 8:165-199, 1995